Delayed Sleep Onset May Affect Insulin Resistance in Women

The study supports previous findings that hyperarousal of the inflammatory system may contribute to insulin resistance.

Women who have difficulty falling asleep are more likely to develop insulin resistance leading to Type 2 diabetes, according to results published recently in Sleep Medicine.1

Using cross-sectional data collected between 2004 and 2009 from the Midlife Development in the United States (MIDUS) II biomarker project, investigators from South Korea and the United States collaborated to evaluate the impact of sleep and inflammatory markers on insulin resistance. The study cohort included 374 community-based participants (138 men and 236 women) in Madison, WI, who agreed to wear a Mini Mitter Actiwatch-64 wrist activity monitor for 1 week while they underwent a sleep study, which included keeping a sleep journal. Objective measurements taken via actigraphy from the Actiwatch included total sleep time (TST), sleep onset latency (SOL), and wake after sleep onset (WASO).

Specific indicators emerged through different analyses that were associated with increased insulin resistance in both genders: univariate analysis showed a link between higher body mass index (BMI), the presence of diabetes, higher SOL, shorter TST, and inflammatory cytokines, while multivariate regression analysis showed a correlation only to higher BMI, the presence of diabetes, and elevated C-reactive protein (CRP) levels. None of the sleep measures studied correlated with insulin resistance.

Various studies have previously demonstrated gender differences in sleep factors contributing to insulin resistance, which according to the authors may point to a greater vulnerability to sleep disturbances among women that is indicative of higher levels of inflammation.2-4

Similar Mechanisms

Contrary to previous research showing that duration of sleep is directly related to insulin resistance (primarily in young men),5-7 the main finding of the current study was that difficulty with sleep onset — which was more common in women — was more significantly associated with insulin resistance than shorter TST, which did not show any correlation.

The authors contend that the current study did, however, support previous findings of hyperarousal of the inflammatory system as a mechanism of insulin resistance, as increased SOL in women was at least partly attributable to an indirect effect of inflammatory cytokines. It also pointed to evidence that sleep onset disturbances, along with other sleep factors, may contribute via multiple mechanisms to insulin resistance in women, and that different factors may produce similar effects in men. The immediate implications are that improvements in sleep onset for women may help reduce risk of Type II diabetes.